Automatic merge from submit-queue (batch tested with PRs 57399, 57751, 57475). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

printFlexPersistentVolumeSource: fix format

**What this PR does / why we need it**:
This PR fixes invalid format.

**Special notes for your reviewer**:
Addresses https://github.com/kubernetes/kubernetes/pull/56460#discussion_r153583731
Fixes #57694

**Release note**:
```release-note
NONE
```

PTAL @liggitt 
CC @simo5